Thanks Big John for your "potted history" of the event that created the Orange Order. But a few more important facts should have been included:

A Dutch King - true enough, Prince William of Orange was married to the sister (Mary) of the deposed Stuart King. The King was deposed by Parliament in the Glorious Revolution of 1688, Glorious because it was accomplished without bloodshed. The deposed Stuart King didn't think it all that Glorious because he then proceeded to try and win his crown back by raising an army in Ireland not to fight for irish independence but to invade the mainland. The army opposing James was a government army and not one predominantly composed of mercenaries. It came from Scotland mainly for two reasons. The first being that immediately prior to the events of 1690 in Ireland, Viscount Dundee, had raised a rebellion in support of James in Scotland and the government of the day raised an army to suppress that rebellion in Scotland (1689). Having a bunch of lads already mustered in Scotland, linked to the close proximity of the two countries made them the obvious choice for the job. James's main supporter (apart from the French) for his attempted management take over was the Duke of Ormonde whose power base was in the North of Ireland so that is where the match was arranged.

The Plantation of Scots into Ulster began far earlier in the 17th century and was started by another Stuart King, James Ist of England and VIth of Scotland. He did this as a way of pacifying what he called his "middle shires" - the area normally referred to as the anglo-scottish border.

What they did after seemed to be pretty much par for the course for those times (irrespective of who the combatants were, or where the action took place) and for a long time afterwards (US actions against the Indian nations late 1870's).